In analyzing the number of different bases in a DNA sample, which result would be consistent with the ­ base-pairing rules?
a. A=G
b. A+G=C+T
c. A+T=G+C
d. A=C

In his work with pneumonia-causing bacteria and mice, Griffith found that

a. The protein coat from pathogenic cells was able to transform nonpathogenic cells.

b. Heat-killed pathogenic cells caused pneumonia.

c. Some substance from pathogenic cells was transferred to nonpathogenic cells, making them pathogenic.

d. The polysaccharide coat of bacteria caused pneumonia.

What is the basis for the difference in how the leading and lagging strands of DNA molecules are synthesized?

a. The origins of replication occur only at the 5′ end.

b. Helicases and single-strand binding proteins work at the 5′ end.

c. DNA polymerase can join new nucleotides only to the 3′ end of a pre-existing strand, and the strands are antiparallel.

d. DNA ligase works only in the 3′→5′ direction.

The elongation of the leading strand during DNA synthesis

a. Progresses away from the replication fork

b. Occurs in the 3′→5′ direction

c. Produces Okazaki fragments

d. Depends on the action of DNA polymerase

In a nucleosome, the DNA is wrapped around

a. Histones

b. Ribosomes

c. Polymerase molecules

d. A thymine dimer

E. coli cells grown on ¹⁵N medium are transferred to ¹⁴N medium and allowed to grow for two more generations (two rounds of DNA replication). DNA extracted from these cells is centrifuged. What density distribution of DNA would you expect in this experiment?

a. One high-density and one low-density band

b. One intermediate-density band

c. One high-density and one intermediate-density band

d. One low-density and one intermediate-density band